David Cameron is to stand down as MP for Witney, triggering a by-election in the Oxfordshire seat, he has announced.
Mr Cameron told ITV News that he had thought "long and hard" over his choice but had ultimately decided that he would be a "distraction" from the work of government.
David Cameron's legacy will be "overshadowed" by his role as the accidental architect of Brexit, according to the former Conservative minister Ken Clarke.
"I'm a friend of David's, so I regret to say, I think for history his legacy will be he's the man who accidentally caused Britain to leave the European Union, he told BBC News.
"There's no getting away from the fact that that will overshadow every other feature of his premiership."
Mr Clarke added that he was "disappointed" by Mr Cameron's decision but said the "chickens came home to roost" after the referendum.
Cameron said he would stay on as Witney MP after resigning as PM - but he said in practice it was an impossible switch.
The former prime minister has stepped down from his position in parliament as he resigned his seat as the MP for Witney.
He rose to lead the country before an equally dramatic downfall after failing to persuade the public to vote to remain in the EU.